Polymeric materials, such as vinyl polymers, and products made therefrom must exhibit resistance to degradation if they are to have any useful commercial value. The degradation can be a partial or total loss of structural integrity, a darkening or discoloration of the product, a loss of flexibility or resilience, or a combination of any of these phenomena. The various types of degradation, above referred to, are promoted or catalyzed by oxygen (air), heat, and light, and in particular, ultraviolet (UV) light.
In order to protect polymeric materials, it has been the practice in the art to add various ingredients or stabilizers to the polymers, or compounds thereof, to prevent or inhibit degradation of finished articles made therefrom. In this regard, see U.S. Pat. No. 4,069,195 and the numerous prior art references cited in the specification which relate to the stabilization of polymeric materials against degradation. These stabilizers work in diverse and complex ways, such that a compound that stabilizes against heat and oxygen degradation in a polymer or resin may not stabilize against light degradation in the same polymer or resin or vice versa. Further, a compound that acts as a stabilizer against oxygen degradation in one type of polymeric material may be relatively inactive in another type of polymeric material. Accordingly, compounds that are stabilizers are further classified as antioxidants, antiozonants, heat stabilizers, and ultraviolet (UV) light stabilizers, depending upon what type of stabilization they demonstrate. In many instances, to obtain optimum protection, a mixture of compounds, each specifically selected to afford maximum protection against a certain type of degradation, is often used. In U.S. Pat. No. 4,100,325 improved weather resistant polymers have improved impact resistance by employing a minimum amount of TiO.sub.2 in the capstock formulation. However, such products are opaque.
One of the more difficult to control of the degradative forces is irradiation of the polymer by UV light. The impact of such irradiation will vary depending upon the intensity and duration of exposure and therefore, may manifest itself only after a prolonged period of time. The irradiation of polymers with UV light can often cause cross-linking of the polymeric materials thereby reducing their resiliency and/or impact resistance. Changes in color and opacity are also often effected by prolonged exposure of the polymeric material to UV light. While many materials are known, and commercially available, as stabilizers against UV light degradation, the degree of protection afforded by such agents is often dependent upon the concentration thereof in the polymeric compound. This presents economic difficulties and affects commercialization since the cost of said stabilizers or agents is very expensive, particularly by comparison to the cost of the polymeric materials they are employed with to reduce UV Light degradation.
Vinyl polymers, and particularly polyvinyl chloride (PVC), compounds without ultraviolet light protection are not stable to the weather. For example, they become tan, brown or black in a hot climate, such as the climate in Arizona, or they rapidly fade or become white in a cold climate, such as the climate in northern Ohio. Known PVC formulations, which are good performers in the weather, contain large amounts of titanium dioxide pigment. This pigment acts as an UV light absorber, thus protecting the PVC against degradation. However, it also makes the polymeric material opaque. In order to get weatherability, or UV light stabilization, in translucent polymeric materials, such as are used in corrugated roofing for patios, and the like, or in transparent polymeric materials, a clear UV light absorber or stabilizer must be used. Thus it can be seen that there is a need to find a clear UV stabilizer for vinyl polymeric materials but also an economic and commercial method of using the same to protect said materials from UV light degradation.